324 PETROLOGICAL ABSTRACTS AND REVIEWS 



which were at perfect equilibrium with each other under the conditions 

 of their formation. Igneous rocks, likewise, may reach a state of 

 equilibrium, and igneous and metamorphic facies may be spoken of 

 together as mineral facies. Mineral facies, therefore, comprise all rocks 

 which have originated under conditions of temperature and pressure so 

 similar that from a definite chemical composition there results the same 

 set of minerals, regardless whether formed by primary crystallization 

 or by metamorphism. 



EsKOLA, Pentti. "On the Igneous Rocks of Sviatoy Noss in 

 Transbaikalia," Overskit av Finska Vetensk.-Soc. Forhand., 

 Vol. LXIII (1920-21), pp. 1-99. Figs. 9. 



This is an abstract from the reports of the Moscowian expedition to 

 Transbaikaha in search of radium in 1914. Two great complexes of 

 rock were found, a granite-granodiorite mass and the injected crystalline 

 schists. The first mass is here and there intersected by lamprophyric, 

 aplitic, and pegmatitic dikes, and there are larger aplitic masses. As 

 the boundary between the granite and the migmatite is approached, the 

 aplitic portions increase, until near the border there is an almost uninter- 

 rupted zone of light gray, aplitic granite. Still farther west the inclusions 

 of crystalline schist become more numerous and the rock grades into 

 migmatite with only occasional veins of granite. Before the intrusion of 

 the granite, the crystalline schists were invaded by diorites and gabbros 

 which are now metamorphosed and foliated, and cut by the later aplites 

 and pegmatites. 



The main igneous complex is called granodiorite, following Iddings, 

 although the alkali feldspar and lime soda feldspar are in nearly equal 

 amounts and therefore, as Eskola clearly recognizes, more rationally 

 quartz-monzonite. The complete mode is not given. The aplitic 

 border has a calculated mode which probably closely approximates the 

 true composition. According to the reviewer's classification it is 227' 

 (new form), consequently a granodiorite-aplite, the plagioclase being 

 almost twice as abundant as the microcline. Two types of "sviatonos- 

 site" are described, one aplitic, but otherwise the two are of practically 

 the same composition. They contain 25-31 per cent potash feldspar, 

 45-48 per cent oligoclase to andesine, 9-10 per cent andradite, and 8-17 

 per cent aegirite-augite and accessories. The author says they are 

 andradite-syenites, but from the proportions of potash feldspar and 

 plagioclase the reviewer would call them andradite-syenodiorites, or, if 

 monzonites are considered in the classification, andradite-monzonites. 

 They fall just over the line in Family 11" (2211"), very near 11'. 



